What is undefined string - Canon Office Equipment & Supplies

I suspect you got this error during the compilation or execution of a program. If that is not the case, disregard what I am rambling on about .
A string is a set of printing characters (letters, numbers, punctuation signs). In some programming languages a string variable can be defined. Once you define a variable as a string, you can store a string in it.
Depending on the language the string must be enclosed between quotation marks or some other separators. As for other variables, string variables have to be defined before they can be called.
Go to the location where the error occurred and check your inputs, arguments you feed to functions, etc.